1 Who has believed what he has heard from us? And to whom has the arm of the Lord been revealed? 2 For he grew up before him like a young plant, and like a root out of dry ground; he had no form or majesty that we should look at him, and no beauty that we should desire him. 3 He was despised and rejected by men, a man of sorrows and acquainted with grief; and as one from whom men hide their faces he was despised, and we esteemed him not.
Isaiah 53:1-3 ESV https://bible.com/bible/59/isa.53.1-3.ESV
Unbelief in the servant was natural because he was an obscure, outwardly unimpressive person in a failed culture. “His generation” was blind (v.8).
ESV Study Bible note on Isaiah 53:2